Photographs taken this morning showed the burned-out shells of at least two vehicles and a tractor-trailer, with gray smoke still rising above the asphalt on an otherwise desolate Interstate 75.

Florida Highway Patrol Lt. Patrick Riordan said the pileups happened around 3:45 a.m. on both sides of I-75 south of Gainesville. All lanes of the interstate — there are three lanes running each direction — remained closed as investigators began trying to figure out exactly what caused the wrecks.

Vehicles were still smoldering, and firefighters sprayed foam to try to put out the fires.

Cars appeared to have smashed into tractor-trailers and, in one case, a motor home. Some cars were badly crushed beneath the wreckage of the larger rigs.